Bevel up blade sharpening question

[ear3]

So I got several blade for my low angle jack plane to sharpen at different angles for different woods.  My question is about the maximum microbevel I can put on a plane blade relative to the primary bevel.  All the blades come with a 25 degree primary bevel.  I don't expect there to be an issue putting a 10 degree secondary bevel on one of them,but say I wanted a much larger angle, something between 40-45 degrees (for a total of 52 to 57 counting the 12 degree bed) to deal with tearout on more figured or sensitive woods.  At that point should I switch the primary bevel to something closer to that upper range (like 35), or is it okay to put a 45 degree secondary bevel on a 25 degree primary bevel?

 

[Wooden Skye]

I have always been taught that the micro bevel should be 5 to 7 degrees.  Then again if you have multiple blades having the micro bevel may not be necessary.

 

[GarryMartin]

I've only ever seen 5-10 degree secondary bevels used.

I've nearly bought this book so many times. Perhaps it would be interesting reading for you?
https://hocktools.wordpress.com/2010/08/25/two-better-than-one/

 

[ear3]

Egad! So many angles. I'll check it out though, thanks. Still working my way through Garrett Hacks book.

I've only ever seen 5-10 degree secondary bevels used.

I've nearly bought this book so many times. Perhaps it would be interesting reading for you?
https://hocktools.wordpress.com/2010/08/25/two-better-than-one/

 

[ear3]

Just called and spoke with Brian directly and ordered the book. Seems like a great guy and super knowledgeable. He just printed up more in case anyone's interested.

 

[flair woodworks]

Micro bevels need to be kept fairly small for bevel down planes.  For bevel up planes, you can go as big as you like.  Think about how the edge is supported by the rest of the blade.

 

[Holmz]

I prefer acute angles.

 

[Steve-Rice]

Ed,

If you bought the Veritas bevel up low angle jack from Lee Valley, they sell blades of different angles at 25, 38 & 50 degrees. I'd prefer that to a micro bevel on a 25 degree blade.  I love this plane, it's a great all around performer.

 

[mouppe]

I always found sharpening a bevel that steeply is quite difficult (I sharpen most things freehand). I prefer to use a scraper plane for this type of situation, or sandpaper. Veritas make an excellent scraper plane and it's inexpensive.

 

[nako]

Another good book on hand planes was by Christopher Schwartz.  He also wrote a good book on hand saws>

 

[derekcohen]

So I got several blade for my low angle jack plane to sharpen at different angles for different woods.  My question is about the maximum microbevel I can put on a plane blade relative to the primary bevel.  All the blades come with a 25 degree primary bevel.  I don't expect there to be an issue putting a 10 degree secondary bevel on one of them,but say I wanted a much larger angle, something between 40-45 degrees (for a total of 52 to 57 counting the 12 degree bed) to deal with tearout on more figured or sensitive woods.  At that point should I switch the primary bevel to something closer to that upper range (like 35), or is it okay to put a 45 degree secondary bevel on a 25 degree primary bevel?

If you plan to use your BU plane (here, a LV LA Jack) for smoothing and want to guard against tearout, then the cutting angle needs to be high, typically around 60 degrees. This could be made of the 12 degree bed and a 48 degree bevel.

To avoid plan tracks, the blade needs a fine camber. With a bevel down plane, bedded at (say) 45 degrees, typically the bevel would be 30 degrees. Now cambering a 48 degree bevel is rather more difficult than cambering a 30 degree bevel as there is significantly more steel to remove.

The answer is to always use a 25 degree primary bevel for BU planes, and then add the camber via a a 48 degree micro secondary bevel. This is a strategy I came up with for Lee Valley many years ago. It remains the recommended method.
http://www.inthewoodshop.com/WoodworkTechniques/TheSecretToCamberinBUPlaneBlades.html

The factory-ground 38- and 50 degree straight blades are fine for tasks that require a straight blade, such as jointing. Otherwise I would simply just purchase the 25 degree blades and add a secondary micro bevel.

What you are advised not to do with a BU blade is to add a back bevel. This will reduce the clearance angle. You can get away with up to 5 degrees, leaving 7 degrees clearance, but this is quite borderline. The Ruler Trick (of David Charlesworth) is only 2/3 of a degree. That is fine to use should you wish to do so.

Regards from Perth

Derek

 

[ear3]

Don't know why I didn't see this at first on their site, but the high angle blade LN makes for the BU jack is simply their standard 25 degree primary bevel blade sharpened with a 50 degree secondary bevel.  So apparently a 25 degree difference between primary and secondary is kosher.